1. field of The Invention
The present invention relates to moving target indicator radar systems, and more particularly to MTI radar systems employing two-pulse short interval techniques.
2. Description of the Prior Art
The patent, textbook and periodical literature describes a wide assortment of MTI radar systems. Fundamentally, MTI radar systems operate by examining signal returns resulting from successive transmitted pulses. Some type of cancellation, applicable to fixed returned signals corresponding to non-moving targets, or some type of filtering is employed to reject signals corresponding to non-moving targets. In the broadest sense, filtering may be said to include a wide variety of discriminatory devices ranging from frequency-chirp matched filters, Doppler component filters, and long period storage devices as used in some types of MTI systems.
A review of the prior art in respect to MTI radar may be conducted by examination and study of Chapter 17 of the text entitled "Radar Handbook" by Merrill Skolnik, a McGraw-Hill book (1970). That reference provides a bibliography of additional references and will serve to acquaint the reader not only with the current state of the MTI art, but also to apprise him of the problems confronted by the designer in that particular art.
Since the present invention makes use of the concepts of transmitted pulse "chirp" and receiving system pulse compression, Paragraph 17.15 of the aforementioned reference is of particular background interest. The reader is also directed to the textbook "Modern Radar Analysis, Evaluation, and System Design" by Raymond S. Berkowitz, a John Wiley and Sons book (third edition, August, 1967). In that particular reference book, the whole of Chapter 2 of Part IV is devoted to the subject of linear f-m pulse compression, which is useful background information in understanding the present invention.
Among the design problems encountered in the MTI systems are the problem of blind speed, antenna scan modulation and clutter fluctuation effects. Super-clutter visibility for targets moving in distributed clutter is also a problem area in which prior art systems have been deficient. The manner in which the present invention solves or eliminates certain significant problems encountered in the prior art will be understood as this description proceeds.